Autoimmune diseases, including autoimmune arthritis, represent significant human diseases of high morbidity and prevalence. Rheumatoid arthritis affects ˜0.6% of the world population (Firestein, G. S., Nature (2003) 423: 356). While the adaptive immune response, involving generation of auto-antibodies which react with tissue antigen, is involved in the etiology and initial propagation of these diseases (Edwards, J. C. et al, New England Journal of Medicine (2004) 350: 2572; Genovese, M. C. et al, New England Journal of Medicine (2005) 353: 1114), the chronic manifestations of tissue and joint damage are mediated in large part by cellular events mediated by the innate immune response (Firestein, G. S., Nature (2003) 423: 356; Paniagua, R. T. et al, Arthritis Research & Therapy (2010) 12: R32). Contributing cell types from the innate immune response which mediate chronic tissue damage include fibroblast-like synoviocytes, macrophages, mast cells, and osteoclasts.
Kinases represent a protein family that play critical roles in mammalian cell function, including cell proliferation, survival, motility, response to growth factors, and secretion of cytokines and other proinflammatory, proangiogenic, and immunomodulatory substances. Thus, elucidation of kinases which mediate these events in fibroblast-like synoviocytes, macrophages, mast cells, and osteoclasts represents a rational approach to new therapies for the treatment of autoimmune diseases.
Imatinib is a marketed kinase inhibitor for the treatment of the cancer chronic myelogenous leukemia (CML, Druker, B. J. et al, New England Journal of Medicine (2001) 344: 1031) and for the treatment of gastrointestinal stromal tumors (GIST, Demetri, G. D., et al, New England Journal of Medicine (2002) 347: 472). Imatinib has also shown benefit in cancer patients co-presenting with autoimmune diseases such as rheumatoid arthritis (Ihara, M. K. et al, Clinical Rheumatology (2003) 22: 362; Eklund, K. K. and Joensuu, H., Ann Medicine (2003) 35: 362; Ames, P. R. et al, Journal of Rheumatology (2008) 35: 1682). The kinases inhibited by imatinib which confer its efficacy in the treatment of CML and GIST are BCR-ABL kinase and c-KIT kinase, respectively. Beyond these two kinases, other kinases inhibited by imatinib include c-FMS, PDGFR-alpha, and PDGFR-beta (Dewer, A. L. et al, Blood (2005) 105: 3127; Fabian, M. A. et al, Nature Biotechnology (2005) 23: 329.
Recent research disclosures have identified c-FMS kinase to be associated with activation of synovial macrophages, PDGFR kinase to be associated with activation of fibroblast-like synoviocytes, and c-KIT kinase to be associated with activation of mast cells (Paniagua, R. T., et al Journal of Clinical Investigation (2006) 116: 2633). c-FMS kinase has also been associated with the proliferation and differentiation of monocytes into macrophages and osteoclasts, which are recruited to mediate joint damage in rheumatoid arthritis (Paniagua, R. T. et al, Arthritis Research & Therapy (2010) 12: R32; Yao, Z. et al, Journal of Biological Chemistry (2006) 281: 11846; Patel, S, and Player, M. R. Current Topics in Medicinal Chemistry (2009) 9: 599; Pixley, F. J. et al, Trends in Cell Biology (2004) 14: 628).
In recent years, the importance of the tumor microenvironment in cancer motility, invasion, and metastasis has become more clearly defined. Specifically, the role of tumor-associated macrophages (TAMs) in tumor progression has been studied. These host (stromal) macrophages are recruited to tumor sites or to pre-metastatic niches to modify the tumor environment and render that environment more conducive to tumor motility, invasion and metastasis. These TAMs are known to express c-FMS receptor tyrosine kinase (also known as CSF-1R) on their surfaces and to rely on signaling through this kinase by binding to the activating ligands CSF-1 (also known as macrophase colony stimulating factor, or MCSF) and interleukin-34 (IL-34). Activation of this c-FMS/MCSF (CSF1-R/CSF-1) signaling axis stimulates monocyte proliferation, differentiation into tumor associated macrophages, and promotion of macrophage cell survival. By stimulating the TAM component of the tumor microenvironment, c-FMS kinase activation is associated with tumor cell migration, invasion, and metastasis (J. Condeelis and J. W. Pollard, Cell (2006) 124: 263; S. Patel and M. R. Player, Current Topics in Medicinal Chemistry (2009) 9: 599). Ablation of CSF-1, the ligand for c-FMS kinase, in mice reduced tumor progression and significantly reduced metastasis in a murine model of breast cancer; whereas overexpression of CSF-1 accelerated metastasis in this model (E. Y. Lin et al, Journal of Experimental Medicine (2001) 193: 727). Furthermore, an interaction between tumor cells and macrophages has been described, wherein macrophage secretion of the tumor growth factor EGF and tumor cell secretion of CSF-1 establish a paracrine loop that promotes tumor migration and invasiveness. This paracrine loop was blocked by administration of an antibody to the c-FMS kinase (J. Wyckoff et al, Cancer Research (2004) 64: 7022). Correlative clinical data have also shown that overexpression of CSF-1 in tumors is a predictor of poor prognosis (R. D. Leek and A. L. Harris, Journal of Mammary Gland Biology Neoplasia (2002) 7: 177; E. Y. Lin et al, Journal of Mammary Gland Biology Neoplasia (2002) 7: 147). c-FMS kinase activation is also required for osteoclast differentiation and activation. Its involvement in mediating bone metastases of various cancers, including breast and prostate cancers, has been reported (S. Patel and M. R. Player, Current Topics in Medicinal Chemistry (2009) 9: 599). High plasma concentrations of CSF-1 have been reported in bone metastatic prostate cancer, implicating activation of osteoclast c-FMS kinase in prostate cancer bone metastases (H. Ide, et al, Human Cell (2008) 21:1). c-FMS inhibitors have been reported to reduce radiographic bone lesions when evaluated in models of metastatic bone disease (C. L. Manthey, et al, Molecular Cancer Therapy (2009) δ: 3151; H. Ohno et al, Mol. Cancer. Therapy (2006) 5: 2634). MCSF-mediated activation of both LYVE-1+ and LYVE1− macrophages also mediates pathological angiogenesis and lymphangiogenesis in murine models of cancer, and blockade of c-FMS signaling resulted in suppression of tumor angiogenesis/lymphangiogenesis (Y. Kubota et al., Journal of Experimental Medicine (2009) 206: 1089). Administration of a CSF-1R inhibitor blocked the recruitment of bone marrow derived TAMs and also bone marrow derived monocytic myeloid-derived suppressor cells (MDSCs) to tumor sites; this blockade led to a significant decrease in tumor angiogenesis and when combined with anti-VEGFR-2 therapy synergistically suppressed tumor growth (S. J. Priceman, et al. Blood (2010) 115: 1461). Irradiation of glioblastoma tumors in mice was shown to cause a temporary decrease in tumor size only to be followed by a rebound tumor vasculogenesis mediated by the recruitment of bone marrow derived monocytes expressing CD11b and F4/80 surface antigens (M. Kioi et al, Journal of Clinical Investigation (2010) 120: 694). CD11b+ and F4/80+ monocytes are also known to express functional c-FMS receptors. Hence, blockade of tumor infiltrating c-FMS+ bone marrow derived monocytes by the use of c-FMS kinase inhibitors offers the potential to prevent tumor rebound vasculogenesis and glioblastoma tumor progression. CSF-1R blockade has also been shown to reverse immunotolerance mechanisms in an immunocompetent murine breast cancer model and promote the appearance of anti-tumor immune programs by upregulating CD8+ T-cell-mediated tumor suppression. Restoration of an anti-tumor immune program was mechanistically linked to c-FMS inhibitor blockade of TAM-mediated Programmed Death Ligand-1 (PDL-1) immunotolerance (D. G. DeNardo, et al. Cancer Discovery (2011) 1: OF52).
Hence, small molecule inhibitors of c-FMS kinase, c-KIT kinase, or PDGFR kinases provide a rational approach to new therapies for the treatment of autoimmune diseases, and to particularly block the chronic tissue destruction mediated by the innate immune system. Inhibition of c-FMS kinase also provides a rational approach to new therapies for the treatment of cancers, especially for the treatment of cancer invasiveness, cancer angiogenesis or vasculogenesis, cancer metastasis, cancer immunotolerance, and for the treatment of cancers prone to bone metastases.
There is a need to provide kinase inhibitors which selectively inhibit kinases causative of the chronic tissue destruction in autoimmune disease (c-FMS, c-KIT, PDGFR), without inhibiting other kinases targeted by marketed cancer therapeutics (ABL, BCR-ABL, KDR, SRC, LCK, LYN, FGFR and other kinases). The present invention discloses novel inhibitors that inhibit c-FMS, c-KIT, and/or PDGFR kinases for the treatment of autoimmune diseases which also exhibit selectivity by not potently inhibiting other kinases including ABL, BCR-ABL, KDR, SRC, LCK, LYN, FGFR, MET and other kinases. The inhibitors of the present invention also find utility in the treatment of other mammalian diseases, including human diseases, mediated by c-FMS, c-KIT, or PDGFR kinases. Such diseases include, without limitation, cancers, autoimmune diseases, and bone resorptive diseases.